organic chemistry - chemrave · polystyrene disposable plates, cups, food containers, packaging...

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ORGANIC CHEMISTRY

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ESTERIFICATION • ACID + ALCOHOL ESTER + WATER

• CONDENSATION RXN

• CONDITIONS: CONCENTRATED SULPHURIC ACID [ CATALYST & DEHYDRATING AGENT]

• NAMING ESTER: 1ST NAME FROM ALCOHOL

2ND NAME FROM ACID

• DRAWING ESTER: 1ST PART: ACID

2ND PART: ALCOHOL

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PHYSICAL PROPERTIES OF ESTERS • Covalent non-polar molecules held together by weak Van der Waals

forces.

• Short chain acids ( C1- C4) produce esters which are oily pleasant smelling liquids. [ fruits, flowers from which perfumes & flavourings are made)

• Long chain acids ( C11 and >) produce esters referred to as fats and oils which are greasy, scentless solids & liquids.

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HYDROLYSIS OF ESTERS • Two types:

1. Acid hydrolysis

2. Alkaline hydrolysis

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ACID HYDROLYSIS • Dilute acid is used to speed up the rxn.

• Ester heated under REFLUX with dilute acid.

• Rxn is reversible.

• What happens:

1. Ester + water [in presence of dil. acid] give acid & alcohol.

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ALKALINE HYDROLYSIS • Ester heated under reflux with dilute alkali

• Rxn is not reversible

• Products can separate easily.

• Rxn takes place in 2 stages:

1. Formation of acid and alcohol

2. The acid formed forms salt and water [in xs alkali]

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Saponification • What is it?

• Process by which soaps are made by the hydrolysis of natural esters.

• Conditions: conc. Sodium hydroxide solution.

• LET’S GO TO THE BOARD!!!!!!!!!!!

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Organic Chemistry

POLYMERS

Many + Parts

Latin: Plasticus, that which can be molded

This name hints at how polymers are made

This name honors plastics useful property of being easily molded

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Definition of a POLYMER

• Polymers are macromolecules formed by linking together thousands of small molecules called MONOMERS

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Polymers are classified according to how they are made • 1. Addition polymers made by ADDITION POLYMERISATION

• Condensation polymers made by CONDENSATION POLYMERISATION

• THEY CAN ALSO OCCURE NATURALLY LIKE COTTON!!

Cotton fiber is mostly cellulose, and cellulose is made of chains of the sugar, glucose linked together a certain way.

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POLYMERISATION

Addition

•Made from unsaturated monomers

•One product formed

•No atoms/molecules lost in the process

Condensation

•Made from monomers with a different composition to theirs

•Polymer formed, along with water/ small molecules

•Loss of small molecules-e.g. water

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Plastics made in ADDITION polymerisation Name of polymer Structure of monomer Used to make

Polythene Packaging, plastic bags, plastic film, plastic wrap

Polystyrene Disposable plates, cups, food containers, packaging material, heat insulator in buildings

PVC/ polyvinylchloride

Rain coats, upholstery, suitcase coverings, plumbing fittings, water pipes, insulation of electric wires

Polypropene Plastic containers- buckets, food containers, bowls, coolers, hinges for lids

Teflon Non-stick coatings for irons and pots

Perspex Glass substitute in aircrafts windows, reflectors on vehicles, sign boards

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Polymerisation

CONDENSATION

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Naturally Occurring: PROTEINS

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Synthetic/ man-made condensation polymers:

• Nylon

• Terylene

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Condensation Polymers are grouped based on the type of linkage between the monomer units 1. Polyamides

amide linkage

2. Polyesters

3. Polysaccarides ---O--- glycosidic linkage

Nylon was discovered in 1935. The name nylon is

derived from two cities where it was discovered namely

New York (NY) and London (LON).

Nylon is used in clothes, shoes, jackets, belts, and accessories. It’s not surprising a magazine is named after this polymer. Where did nylon get its name?

We say certain polymers are man-made, but the truth is they make themselves. Humans only have to get the ingredients near each other. The chemicals will assemble themselves.

Two ingredients are mixed and a solid begins to form at the junction between the two layers of liquid.

Hot nylon spaghetti can be extracted.

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Uses of Condensation Polymers Type of Polymer Example Uses

Synthetic polyamide Nylon Fibres for clothing, ropes, fishing lines, nets

Protein Keratin Growth & repair tissues, muscles, hair, nails, enzymes

Polyester Terylene Fibres for clothing, boat sails & fishing lines

Polysaccaride Starch Food reserves in plants, food source for animals